Question

Can anyone explain all the answer?

1. Horizontal force needed to keep a sled moving along dry (it means not wet) horizontal surface is 10 N. You increase this force up to 20 N. Neglect air resistance.  What can you say about character of motion of a sled now?

a. Sled will continue to move with the same speed.

b. Sled will accelerate for a while up to higher speed and then move with constant, higher speed.

c. Sled will accelerate indefinitely.

d. Sled will move with constant speed two times greater than initial.

2. You try to move a refrigerator of weight 2000 N applying force of 500 N. Refrigerator does not move. The force of friction acting of refrigerator is:

a. 2000 N

b. More than 500 N but less than 2000 N

c. Slightly less than 500 N

d. 500 N

e. Zero.

3. A person rides an elevator standing of a bathroom scale (people are doing strange things). Elevator moves up with constant velocity. What will be the reading of a bathroom scale?

a. more than mg

b. mg

c. less than mg

d. zero

4. Some force acts on an object sitting on the horizontal surface and it accelerates. We increase force twice and perform experiment again. If surface is frictionless, the acceleration of an object will increase:

a. Less than two times

b. Exactly twice

c. More than twice

d. Stays the same.

5. An object is sitting at rest on a horizontal table. Which one of Newton’s laws predicts that normal force acting on this object is equal in magnitude and opposite in direction to the force of gravity (weight) acting on this object?

a. First

b. Second

c. Third

d. Law of gravitation.

Answer 1